Displacing device

ABSTRACT

A displacement device for fluids, in particular liquids has linearly movable displacement bodies which dip into pump chambers and are connected via respectively one connecting rod to crank pins of an externally driven crank shaft, wherein at least two groups of displacement bodies are provided. All the groups each have the same number of displacement bodies and the crank pins for the displacement bodies are arranged distributed around the crank shaft at the same angular distances. The crank pins assigned to one group are arranged with respect to those of the other group each offset by an offset angle β around the crank shaft. Furthermore, the displacement bodies of each group are arranged offset in the axial direction of the crank shaft with respect to those of the other groups and the group displacement bodies are each arranged around the crank shaft at a group offset angle γ with respect to one another. The displacement device enables low pressure pulsations.

The invention relates to a displacement device for fluids, in particular liquids, comprising displacement bodies which dip linearly into the displacement device, namely into cylindrical pump chambers in a pump housing which are each in fluidic communication via a suction valve and a pressure valve, wherein the displacement bodies are each connected via a connecting rod to crank pins of an externally driven crank shaft.

Displacement pumps are known by means of which water can be brought to pressures of several hundred bar. Such pressurized water is used, for example, to descale rolled steel blocks or strips in order to achieve rolled products with high, uniform surface quality.

When using displacement pumps with linearly movable displacement bodies, hereinafter also called plungers, pressure pulsations unavoidably occur which should be kept as small as possible in order to ensured desired uniformity of the descaling of the rolled products. In conventional displacement pumps the cylinders for the displacement bodies are arranged in series in the pump housing. Studies made by the applicant have shown that in such a series arrangement the pressure pulsations become smaller with increasing odd number of cylinders than with an even number of cylinders. However, obstacles to the use of a large odd number of cylinders, e.g. seven cylinders, are the large installation length, the poor mass balance and the non-uniform loading of the crank shaft.

The invention is based on the object of providing a displacement device of the type described initially which leads to few pressure pulsations.

This object is solved by patent claim 1, wherein for a displacement device according to the invention

-   -   at least two groups of displacement bodies are provided,     -   all the groups each have an equal number of displacement bodies,     -   the crank pins for the displacement bodies are arranged         distributed around the crank shaft at the same angular distances         α,     -   the crank pins assigned to one group are arranged around the         crank shaft with respect to those of the other groups in each         case offset by an offset angle β,     -   the displacement bodies of each group are arranged in the axial         direction of the crank shaft offset with respect to those of the         other groups and     -   the groups of displacement bodies are each arranged offset to         one another by a group offset angle γ around the crank shaft.

A particularly compact design can be achieved here if two groups of displacement bodies are provided and the displacement bodies of one group are arranged alternately with the displacement bodies of the other group in the axial direction of the crank shaft.

With this arrangement it is possible to provide the displacement bodies in a V or boxer arrangement.

With regard to better compensation of the mass forces, it is advantageous if the two groups of displacement bodies are arranged in a boxer arrangement, wherein the group offset angle is 180° but can also be modified, e.g. can be 150°. In a boxer arrangement the stressing of the crank shaft is minimized compared to a series arrangement with an odd number of displacement bodies.

In a displacement device designed with two groups of displacement bodies according to the invention, each group comprises three displacement bodies each arranged at the angular distance α of 120° distributed around the crank shaft. An offset angle β of 30° of the crank pins assigned to the first group with respect to those of the second group results in a particularly low pressure pulsation here.

The formulated object can also be solved by a displacement device of the type described initially in which

-   -   a drive is provided with two opposite output shaft ends to which         respectively one crank shaft of a displacement pump is coupled,         which in each case comprises a group of displacement bodies,     -   the two groups of displacement bodies have an equal number of         displacement bodies,     -   the crank pins for the displacement bodies of each group are         arranged offset with respect to one another around the         appurtenant crank shaft at the same angular distances α and     -   the crank pins of one group are arranged offset with respect to         those of the other group by an offset angle β around the         appurtenant crank shaft.

Further advantageous embodiments of the invention with a common drive for two displacement pumps are specified in subclaims 7 to 12.

The invention is explained in detail hereinafter with reference to schematic drawings with further details. In the figures:

FIGS. 1a and 1b shows the side view and front view of a crank shaft with two groups of three displacement bodies each attached thereto in boxer arrangement with a group offset angle γ of 180° in a displacement pump according to the invention;

FIG. 2 shows the front view of a modified displacement pump according to FIG. 1a , here however with a group offset angle γ of 150°;

FIG. 3 shows the crank shaft according to FIG. 1 or 2 without displacement bodies in side view;

FIGS. 4 and 5 shows two schematic views of the crank pin arrangements of the crank shaft according to FIG. 2 and specifically

FIG. 4 shows the crank pin arrangement of a first group of three displacement bodies and

FIG. 5 shows the crank pin arrangement of the second group of three displacement bodies turned through an offset angle β with respect to this;

FIGS. 6a, b and c show examples for the crank pin positions of a displacement pump according to FIGS. 1a, 1b and 2 in three different rotational positions of the crank shaft;

FIG. 7 shows three diagrams arranged one above the other for an arrangement according to FIGS. 1a and ab in each case as a function of a crank angle between 0 and 360°, namely in the upper diagram six speed curves for the speed of the fixed displacement bodies, in the middle diagram the conveying volume and in the lowest diagram the pressure pulsations;

FIG. 8 shows a perspective view of parts of another displacement device according to the invention with a common drive for two displacement pumps;

FIG. 9 shows a partial view of the displacement device according to FIG. 8.

FIGS. 1a and 1b show in a side view and a front view of a crank shaft 10 with two opposite groups A, B of displacement bodies or plungers 1, 3, 5 (group A) and 2, 4, 6 (group B) mounted thereon. The plungers of group A are arranged alternately to those of group B in the axial direction of the crank shaft as can be seen from FIG. 1a . The groups A and B are arranged offset with respect to one another by a group offset angle γ of 180° in boxer arrangement. The angle γ according to FIGS. 1a and 1b is 180°, but can differ from this.

The crank shaft 10 and the plungers 1 to 6 form part of a displacement pump whose housing and further parts are not shown; it is understood however that the plungers 1 to 6 are guided in a slidable and sealed manner in cylindrical pump chambers of the usual design, wherein the pump chambers are in fluidic communication via respectively one suction valve and one pressure valve in order to bring a fluid, e.g. water to high pressures.

FIG. 3 shows the crank shaft 10 alone. At its right end in FIG. 3 it is provided with a drive spigot 17 by means of which it can be coupled to an output shaft of a drive (not shown) such as an electric motor. Furthermore it has two bearing bosses 18, 19 arranged at a distance, by means of which it is rotatably mounted in bearings of the pump housing, not shown. In the spacing between the two bearing bosses, crank pins 11 to 16 are arranged adjacent to one another in the axial direction. The three crank pins in each case of the two groups are each arranged distributed at an angular distance α=120°. The reference numbers 1 to 6 for the plungers not shown in FIG. 3 here relate to the assignment to the appurtenant crank pins 11 to 16, i.e., 1 to 11, 2 to 12 etc. The plungers 1 to 6 are connected to these crank pins via connecting rods 20 in the usual manner by means of crossheads 21. The three crank pins 12, 14, 16 are according to FIG. 5 arranged on the crank shaft offset with respect to the crank pins 11, 13, 15 by an offset angle β. This has the result that the displacement effect of the even-numbered plungers 2, 4, 6 is not set at the same time as that of the odd-numbers plungers 1, 3, 5 but takes place offset in time by β=30°. This has the result that the pressure pulsations are equalized over the revolution of the crank shaft, as is explained in detail in the following. On this matter, reference is made to FIGS. 6a, 6b and 6c as well as to FIG. 7.

FIGS. 6a, b and c show the crank shaft according to FIGS. 1 to 5 in the three rotational positions 0°, 60° and 90°. Similarly to the diagram in FIGS. 4 and 5, the crank pins 11 to 16 are symbolized by circles which are shown smaller here than in FIGS. 4 and 5 for simpler representation. Other than in these figures however, all six crank pins are shown here in each case in the three FIGS. 6a, 6b and 6c in order to make the tracking of the crank pins by the offset angle β clear. A reference number 1 to 6 designating one of the respective plungers is indicated in each circle. Plungers with odd reference numbers 1, 3 or 5 belong to group A and convey upwards in FIGS. 1a, 1b and 2 whereas plungers with even reference numbers 2, 4 or 6 belong to group B and convey downwards. The square plunger symbol in the respective circle above or below the plunger reference number represents the direction of action of the relevant plunger. Pressurized conveying plungers are identified by hatched lines. Plungers without hatched lines are located in the suction stroke and are pressure-free.

In the uppermost diagram in FIG. 7, the speed curves g1 to g6 of the individual plungers 1 to 6 are shown as a function of the crank angle of the crank shaft from 0 to 360°, wherein the reference to the respective plunger is characterized by its reference number. Thus curve g1 pertains to plunger 1, curve g2 to plunger 2 etc.

Plungers at the upper dead point OT or lower dead point UT have the speed zero, and therefore intersect the crank angle axis x. Here the conveying process begins or ends. For example, the plunger 1 is located at crank angle zero in UT and begins to convey with increasing conveying quantity. The plunger 2 is already located in the conveying state with increasing conveying quantity at crank angle zero.

At crank angle 60° according to FIG. 6b , the plunger 3 is located in the upper dead point OT and the speed curve g3 intersects the crank angle axis in a descending manner whilst plunger 2 reaches the maximum speed and conveys at maximum capacity.

At 90° plunger 1 conveys at the highest speed at maximum capacity whilst plunger 6 has reached the speed 0 m/s in OT etc.

Curve f in the middle diagram of FIG. 7 shows the periodic fluctuation of the conveyed fluid amount in l/min between approximately 1550 l/min and 1610 l/min achieved with a displacement pump according to FIGS. 1 to 5.

Finally curve d in the lowest diagram in FIG. 7 shows the pressure pulsation of the conveyed liquid which fluctuates between 375 bar minimum pressure and 400 bar maximum pressure.

This constitutes a very low pressure pulsation which is small than that which can be achieved with a conventional displacement pump with seven pumps in series.

FIGS. 8 and 9 show an alternative displacement device wherein FIG. 9 shows the right half of the device according to FIG. 8 in a side view according to FIG. 1a . In FIGS. 8 and 9 the same reference numbers as in FIGS. 1 to 6 are used for the same parts or those having the same effect.

As FIG. 8 shows, the displacement device possesses an electric motor 30 as drive whose continuous output shaft (not visible) is coupled with its output shaft ends 34 each to a crank shaft 10 of its own displacement pump 31, 32. Thus, a unit is formed comprising a central drive 30 and two displacement pumps 31, 32 aligned with this, which are mounted in a flying manner on the motor 30. Each displacement pump has a plunger group A with three plungers arranged in series, namely group A with plungers 1, 3, 5 (left in FIG. 8) and group B with plungers 2, 4, 6 (right of electric motor 30 in FIGS. 8 and 9). All the plungers 1, 3, 5 and 2, 4, 6 are each arranged in series and in the same vertical plane E. The crank pins 11, 13, 15 of the crank shaft 10 of group A are arranged according to FIG. 4 in the same plane E as the plungers 1, 3, 5. However, the crank pins 12, 14, 16 of the crank shaft 10 of group B as in FIG. 5 are arranged offset by an offset angle β=30° on the second crank shaft 10. As a result of this offset, a lower pressure pulsation can be achieved with a displacement device according to FIGS. 8 and 9 than with a conventional displacement pump with an odd number of plungers.

The invention is not restricted to the embodiments shown. Thus, each plunger group of one embodiment according to FIGS. 1 to 9 can also have more than three plungers for each group. It is also possible to have more than three crank pin arrangements distributed uniformly around a common crank shaft, e.g. four crank pins, which are distributed around the circumference of the crank shaft by an angular spacing α=90°. The offset angle β can also be smaller than or greater than 30°.

The features disclosed in the preceding description, the claims and the drawings can be important, both individually and in any combination, for the implementation of the invention in its various configurations.

REFERENCE LIST

-   A, B Plunger group -   1 to 6 Displacement body, plunger -   10 Crank shaft -   11 to 16 Crank pin -   17 Drive end -   18, 19 Bearing boss -   20 Connecting rod -   21 Cross head -   α Angular distance of the plungers of one group -   β Offset angle of the crank pins of one group to those of the other     group -   γ Group offset angle of the plunger groups -   30 Electric motor -   31, 32 Displacement pump -   34 Output shaft end -   E, F Plane -   x Crank angle axis -   f Conveying quantity curve -   d Pressure pulsation curve -   g1 to g6 Speed curves 

What is claimed is:
 1. A displacement device for fluids, in particular liquids, comprising linearly movable displacement bodies which dip into the displacement device and are each connected via a connecting rod to crank pins of an externally driven crank shaft, wherein at least two groups (A; B) of displacement bodies are provided, all the groups each have an equal number of displacement bodies, the crank pins for the displacement bodies are arranged distributed around the crank shaft at the same angular distances (α), the crank pins assigned to one group (B) are arranged around the crank shaft with respect to those of the other groups (B) in each case offset by an offset angle (β), the displacement bodies of each group (B) are arranged in the axial direction of the crank shaft offset with respect to those of the other groups (A) and the groups (A; B) of displacement bodies are each arranged offset to one another by a group offset angle (γ) around the crank shaft.
 2. The displacement device according to claim 1, characterized in that two groups (A; B) of displacement bodies are provided and that the displacement bodies of one group (B) are arranged alternately with the displacement bodies of the other group (A) in the axial direction of the crank shaft.
 3. The displacement device according to claim 2, characterized in that the two groups (A; B) of displacement bodies are arranged in a boxer arrangement, wherein the group offset angle (γ) is 180°.
 4. The displacement device according to claim 1, characterized in that each group comprises three displacement bodies each arranged at the angular distance (α) of 120°.
 5. The displacement device according to claim 1, characterized in that the offset angle (β) is 30°.
 6. A displacement device for fluids, in particular liquids, comprising linearly movable displacement bodies which dip into the displacement device and are each connected via a connecting rod to crank pins of an externally driven crank shaft, wherein a drive is provided with two opposite output shaft ends to which respectively one crank shaft of a displacement pump is coupled, which in each case comprises a group (A; B) of displacement bodies, the two groups (A; B) of displacement bodies have an equal number of displacement bodies, the crank pins for the displacement bodies (A; B) of each group are arranged offset with respect to one another around the appurtenant crank shaft at the same angular distances (α); and the crank pins of one group (B) are arranged offset with respect to those of the other group (A) by an offset angle (β) around the appurtenant crank shaft.
 7. The displacement device according to claim 6, characterized in that the output shafts and the crank shafts are aligned with one another.
 8. The displacement device according to claim 6, characterized in that the two groups (A; B) of displacement bodies are arranged offset with respect to one another around the crank shafts by a group offset angle (γ).
 9. The displacement device according to claim 6, characterized in that each group (A; B) comprises three displacement bodies which are each arranged distributed around the appurtenant crank shaft at the angular distance (α) of 120°.
 10. The displacement device according to claim 6, characterized in that the offset angle (β) of the crank pins of each crank shaft is 30°.
 11. The displacement device according to claim 6 characterized in that the drive is an electric motor.
 12. The displacement device according to claim 11, characterized in that the electric motor has two opposite output shaft ends which are aligned with one another and which form the end parts of a continuous electric motor shaft. 